#include <iostream>
using namespace std;
 
class Base
{
public:
    Base() {}      
};
 
// Forward declaration
class Derived1;
 
class Derived2 : public Base
{
	friend class Derived1;
 
public:
    Derived2() : Base() {}
private:    
    Derived1 *ptr;
 
};
 
class Derived1 : public Base
{
public:
    Derived1(Derived2& obj) : Base(), ptr(&obj) {
    	obj.ptr = this;
    }
private:
    Derived2 *ptr;
};
 
int main() {
 
	Derived2 obj2;
	Derived1 obj1(obj2);
 
 
 
	return 0;
}

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